1. Technical Field
The present invention relates to a method and system for network processing in general, and in particular to a method and system for providing interoperability between network clients within a local-area network. Still more particularly, the present invention relates to a method and system for providing interoperability between multiple versions of LUNI within an Asynchronous Transfer Mode emulated LAN.
2. Description of the Prior Art
For several years, the embedded base of many communication networks have been established according to the IEEE 802 LAN standards, such as the IEEE 802.3 standard for Ethernet LANs and the IEEE 802.5 standard for Token-Ring LANs. These communication networks are considered to be xe2x80x9cconnectionlessxe2x80x9d because data packets can be exchanged within these networks without establishing a layer-2 connection under the seven-layer networking reference model established by the International Organization for Standardization (ISO). In addition, the applications within these communications networks typically reside on top of a layer-2 protocol and a layer-3 protocol, such as Medium Access Control (MAC) and Internet Protocol (IP), respectively.
With the advent of Asynchronous Transfer Mode (ATM) technology, which offers the advantages of fixed-size cell switching, sealablility from a few megabits to hundreds of megabits, the ability to offer guaranteed quality of service on a per connection basis, etc., it is desirable to interconnect a LAN which is still under one of the IEEE 802 LAN standards (or so-called a Legacy LAN) with communication networks that are equipped with ATM capabilities. In order to take advantage of the vast base of existing LAN application software, the ATM Forum has defined an ATM service, commonly known as a LAN Emulation service, that emulates services of existing LANs across an ATM network and can be supported via a software layer in end systems such as workstations, servers, bridges, etc. The LAN Emulation service enables an end system to connect to an ATM network and allows any software application within the end system to interact with other systems within the ATM network as if the end system is attached to a traditional LAN.
In January 1995, the ATM Forum promulgated the LAN Emulation over ATM Version 1xe2x80x94LUNI Specification (LUNI-1 specification) to define a LAN Emulation User Network Interface (LUNI) for LAN Emulation (LE) clients within an ATM emulated LAN, the pertinent portion of which is incorporated by reference herein. Subsequently, in July 1997, the ATM Forum approved the LAN Emulation over ATM Version 2xe2x80x94LUNI Srecification (LUNI-2 specification), the pertinent portion of which is incorporated by reference herein. The LUNI-2 specification intends to provide additional extensions for improving the capabilities of LE clients while maintaining compatibility with existing LUNI-1 LE client implementations. One of the defined LUNI-2 extensions is to allow LE clients to append a variable length field, known as a Type/Length/Values (TLVs) field, to the end of some LE Control Frames. On the other hand, with the exception of LE Configuration Server (LECS) Configurations Request and Response Control Frames, the LUNI-1 specification does not define any TLVs field for LE Control Frames. In fact, all LUNI-1 LE Control Frames are specified with a fixed-length of 108 bytes.
Because of the above-mentioned differences between the LUNI-1 specification and the LUNI-2 specification, interoperability problems may arise between LUNI-1 LE clients and LUNI-2 LE clients in a mixed emulated LAN environment. For example, a LUNI-1 LE client may neglect to transmit each reserved field with a zero value because some of these reserved fields are typically not utilized by LUNI-1 LE clients, and LUNI-2 LE clients will interpret the data transmitted in these reserved fields and attempt to perform operations as dictated by the LUNI-2 specification. As another example, a LUNI-1 LANE client may neglect to properly process an LE Control Frame originated by a LUNI-2 LE client that is not 108 bytes in length, such as discarding the entire LE Control Frame due to its non-conformance with the LUNI-1 specification. These kinds of interoperability problems could cause various problems to the network depending on the robustness and the level of adherence of LUNI-1 LE clients to the LUNI-1 specification during the LE client implementation. Consequently, it would be desirable to provide a method and system for improving the interoperability between network clients having different versions of local-area network (LAN) emulation user network interface (LUNI) from each other within an Asynchronous Transfer Mode emulated LAN.
In accordance with a method and system of the present invention, a mixed ATM emulated LAN includes multiple LAN emulated clients (LE clients) having different versions of LAN Emulation User Network Interface (LUNI), such as a first version LUNI and a second version LUNI. The mixed ATM emulated LAN is served by a LAN Emulation Server (LES), a Broadcast and Unknown Server (BUS), and a LAN Emulation Configuration Server (LECS). When an LE Control Frame is being sent by an LE client having a second version LUNI, a determination is made as to whether or not the LE Control Frame will be received by an LE client having a first version LUNI. In response to a determination that the LE Control Frame sent by the LE client having a second version LUNI will be received by an LE client having a first version LUNI, the LE Control Frame is copied, and the copied LE Control Frame is converted to an LE Control Frame with a format that is readable by the LE client having a first version LUNI.
All objects, features, and advantages of the present invention will become apparent in the following detailed written description.